The present invention relates to a semiconductor circuit component which can be driven when an externally provided switch unit is turned on so that a power supply voltage is supplied to the semiconductor circuit component.
A mechanical relay has been heretofore mainly used for the ON/OFF control of a power supply voltage supplied to an on-vehicle electrical component. That is, as shown in FIG. 6, a mechanical relay 101 has a relay coil 102, and relay contacts 103. One terminal T1 of the relay coil 102 is connected to a +B terminal of a battery power supply through a switch 104 while the other terminal T2 of the relay coil 102 is grounded. A terminal T3 of corresponding one of the relay contacts 103 is connected to the one terminal T1 of the relay coil 102 while a terminal T4 of the other of the relay contacts 103 is connected to one end of a load L 105 which has its other end grounded. In this relay circuit, when the power supply side switch 104 is turned on, the relay contacts 103 closed to drive the load 105.
There is another case where, as shown in FIG. 7, the one terminal T1 of the relay coil 102 is connected to the +B terminal of the battery power supply while the other terminal T2 of the relay coil 102 is grounded through a switch 106. Incidentally, the connection of the terminals T3 and T4 of the relay contacts 103 is the same as shown in FIG. 6. In this relay circuit, when the ground side switch 106 is turned on, the relay contacts 103 are closed to drive the load 105.
There is a further case where, as shown in FIG. 8, the one terminal T1 of the relay coil 102 is connected to the +B terminal of the battery power supply through a switch 107 while the other terminal T2 of the relay coil 102 is grounded through a switch 108. Also in this case, the connection of the terminals T3 and T4 of the relay contacts 103 is the same as shown in FIG. 6. In this relay circuit, when the power supply side switch 107 and the ground side switch 108 are turned on simultaneously, the relay contacts 103 are closed to drive the load 105. Incidentally, any one of the relay circuits is formed by mounting the mechanical relay 101 on bus bar terminals of a bus bar circuit board received in an electric connection box.
On the other hand, a semiconductor circuit component 109 having a switching function superior to that of the mechanical relay in terms of reduction in size and cost, and increase in reliability has been developed as schematically shown in FIG. 9 with the rapid advance of the semiconductor producing technique in recent years and has been used widely. The semiconductor circuit component 109 has an MOS-FET 110, and a control signal supply circuit 111 including a charging pump circuit for supplying a control signal to a gate G of the MOS-FET 110. A power input end 112 of the control signal supply circuit 111 and a drain D of the MOS-FET 110 are both connected to a first externally leading-out terminal T11, a ground end 113 of the control signal supply circuit 111 is connected to a second externally leading-out terminal T12, and a source S of the MOS-FET 110 is connected to a third externally leading-out terminal T13.
In the semiconductor circuit component 109 configured thus, a switching operation approximating that of the relay circuit shown in FIG. 6 can be made when, for example, the first externally leading-out terminal T11 is connected to the +B terminal of the battery power supply through a switch, the second externally leading-out terminal T12 is grounded and the third externally leading-out terminal T13 is connected to one end of a load having its other end grounded. Alternatively, a switching operation approximating that of the relay circuit shown in FIG. 7 can be made when the first externally leading-out terminal T11 is connected to the +B terminal of the battery power supply, the second externally leading-out terminal T12 is grounded through a switch and the third externally leading-out terminal T13 is connected to a load.
Alternatively, a switching operation approximating that of the relay circuit shown in FIG. 8 can be made when the first externally leading-out terminal T11 is connected to the +B terminal of the battery power supply through a switch, the second externally leading-out terminal T12 is grounded through a switch and the third externally leading-out terminal T13 is connected to a load. Accordingly, in any relay circuit, it may be considered that the semiconductor circuit component can be designed to take the place of the mechanical relay 101 directly without any substantial change of the circuit configuration of the bus bar circuit board.
In each of the switches 104, 105, 106, 107 and 108 externally provided as shown FIGS. 6, 7 or 8, leakage resistance, for example, of about 10 Kxcexa9 may be generated between contacts due to dew drops. In the case where the mechanical relay 101 is used as shown in each of FIGS. 6, 7 and 8, the mechanical relay 101 never operates with such a small value of leakage resistance because the current flowing in the relay coil 102 is too small. In the case of a circuit using the semiconductor circuit component 109, however, the circuit impedance generated between the first and second externally leading-out terminals T11 and T12 is considerably higher than the leakage resistance generated between the contacts of the switch. Accordingly, if leakage resistance is generated between the contacts of the switch connected to the first or second externally leading-out terminal T11 or T12 side due to dew drops, electrical conduction may be made substantially between the contacts of the switch as if the switch were turned on. As a result, there is a risk that the semiconductor circuit component 109 operates to allow the load 105 to malfunction. Hence, there was a problem that the semiconductor circuit component was difficult to take the place of the mechanical relay directly in the ON-OFF control circuit of the on-vehicle electrical component.
The invention is devised upon such circumstances and an object of the invention is to provide a semiconductor circuit component in which the operation of a load can be switched in response to the ON/OFF operation of a switch unit externally provided in the same manner as in the prior-art mechanical relay and in which the malfunction of the load caused by leakage resistance of the switch unit can be avoided.
(1) To achieve the foregoing object, in accordance with the invention, there is provided a semiconductor circuit component capable of being driven when an externally provided switch unit is turned on to thereby supply a power supply voltage to the semiconductor circuit component, the semiconductor circuit component having: a load-control semiconductor switching device with a control terminal; a control signal supply circuit for supplying a control signal to the control terminal of the load-control semiconductor switching device to thereby drive the load-control semiconductor switching device; and a drive control circuit for controlling drive in a manner so that, only when the switch unit is turned on, a power supply voltage is supplied from the drive control circuit to the control signal supply circuit to make the control signal supply circuit output the control signal.
In this configuration, only when the switch unit is turned on, the control signal supply circuit is driven to supply a control signal to the control terminal of the load-control semiconductor switching device to thereby make the load-control semiconductor switching device electrically conductive. For this reason, the control signal supply circuit is not driven even if leakage resistance is generated between contacts of the switch unit due to dew drops when the switch unit is not turned on. As a result, the load can be prevented from malfunctioning due to the externally provided switch unit, so that the semiconductor circuit component can take the place of the mechanical relay.
(2) Further, according to the invention, in the semiconductor circuit component as in (1), preferably, the drive control circuit is disposed between a power supply and a ground and in series with the switch unit, so that only when the switch unit is turned on, the power supply voltage is supplied from the drive control circuit to the control signal supply circuit.
In this configuration, only when the switch unit is turned on, the drive control circuit is supplied with the power supply voltage. Hence, the drive control circuit is driven to supply the power supply voltage to the control signal supply circuit.
(3) Further, according to the invention, in the semiconductor circuit component as in (2), preferably, the drive control circuit includes: a drive-control semiconductor switching device with a control terminal; and a voltage supply circuit for supplying a drive voltage to the control terminal of the drive-control semiconductor switching device when the switch unit is turned on and a power supply voltage having a rated value is supplied to the voltage supply circuit; and the drive-control semiconductor switching device performs drive control so that the power supply voltage is supplied from the drive-control semiconductor switching device to the control signal supply circuit when the drive voltage is supplied to the drive-control semiconductor switching device from the voltage supply circuit to drive the drive-control semiconductor switching device.
In this configuration, even if leakage resistance is generated between contacts of the switch unit due to dew drops when the switch is not turned on, a voltage drop occurs in the leakage resistance so that the power supply voltage having the rated value is not supplied to the voltage supply circuit. As a result, the drive-control semiconductor switching device is not made electrically conductive, so that the control signal supply circuit is not driven. Accordingly, the load can be prevented from malfunctioning due to the externally provided switch unit, so that the semiconductor circuit component can take the place of the mechanical relay.
(4) Further, according to the invention, in the semiconductor circuit component as in (3), preferably, the voltage supply circuit includes a voltage dividing circuit for dividing the power supply voltage supplied through the switch unit and a voltage suppressing circuit for suppressing a partial voltage into a predetermined value, the partial voltage being obtained by the voltage dividing circuit.
In this configuration, even if the power supply voltage with a large value is supplied from the battery power supply due to the turning on of the switch unit, a voltage having a predetermined value is supplied to the control terminal of the drive-control semiconductor switching device by the function of the voltage suppressing circuit so that the drive-control semiconductor switching device is made electrically conductive in a stable state. Further, in the case where leakage resistance is generated between contacts of the switch unit due to dew drops when the switch unit is not turned on, a voltage drop occurs in the leakage resistance so that only a power supply voltage having a small value is allowed to be supplied to the voltage dividing circuit and, further, the power supply voltage with the small value is divided. As a result, the drive-control semiconductor switching device is not made electrically conductive, so that the control signal supply circuit is not driven. Accordingly, the load can be prevented from malfunctioning due to the externally provided switch unit, so that the semiconductor circuit component can take the place of the mechanical relay.
(5) Further, according to the invention, in the semiconductor circuit component as in (3) or (4), preferably, the drive-control semiconductor switching device has one end connected to a ground end of the control signal supply circuit while the ground end is grounded through the other end of the drive-control semiconductor switching device, so that when a drive voltage is supplied to the drive-control semiconductor switching device from the voltage supply circuit to drive the drive-control semiconductor switching device, the power supply voltage is supplied from the drive-control semiconductor switching device to the control signal supply circuit.
In this configuration, when the drive voltage from the voltage supply circuit is supplied to the drive-control semiconductor switching device to drive the drive-control semiconductor switching device, the ground end of the control signal supply circuit is grounded to thereby supply the power supply voltage to the control signal supply circuit.
(6) Further, according to the invention, preferably, the semiconductor circuit component as in (5) further includes: a first externally leading-out terminal connected to a power input end of the voltage supply circuit while connected to the power supply through the switch unit; a second externally leading-out terminal connected to the other end of the drive-control semiconductor switching device while connected to the ground; a third externally leading-out terminal connected to one end of the load-control semiconductor switching device and to a power input end of the control signal supply circuit while connected to the power supply; and a fourth externally leading-out terminal connected to the other end of the load-control semiconductor switching device while connected to a load.
In this configuration, for example, the first and second externally leading-out terminals can be made to correspond to respective terminals at opposite ends of a relay coil, and the third and fourth externally leading-out terminals can be made to correspond to respective terminals at opposite ends of relay contacts. Hence, the semiconductor circuit component can take the place of the prior-art mechanical relay without any substantial change of the circuit configuration of the bus bar circuit board.
(7) Further, according to the invention, preferably, in the semiconductor circuit component as in (3) or (4), the drive-control semiconductor switching device has one end connected to a power input end of the control signal supply circuit while the power input end is connected to the power supply through the other end of the drive-control semiconductor switching device so that, when a drive voltage is supplied from the voltage supply circuit to the drive-control semiconductor switching device to drive the drive-control semiconductor switching device, the power supply voltage is supplied from the drive-control semiconductor switching device to the control signal supply circuit.
In this configuration, when a drive voltage from the voltage supply circuit is supplied to the drive-control semiconductor switching device to drive the drive-control semiconductor switching device, the power input end of the control signal supply circuit is connected to the power supply to thereby supply the power supply voltage to the control signal supply circuit.
(8) Further, according to the invention, preferably, the semiconductor circuit component as in (7) further includes: a first externally leading-out terminal connected to the other end of the drive-control semiconductor switching device and to one end of the load-control semiconductor switching device while connected to the power supply; a second externally leading-out terminal connected to a ground end of the voltage supply circuit while connected to the ground through the switch unit; a third externally leading-out terminal connected to the other end of the load-control semiconductor switching device while connected to the load; and a fourth externally leading-out terminal connected to a ground end of the control signal supply circuit while connected to the ground.
In this configuration, for example, the first and second externally leading-out terminals can be made to correspond to terminals at opposite ends of a relay coil, and the first and third externally leading-out terminals can be made to correspond to terminals at opposite ends of relay contacts, and the fourth externally leading-out terminal is grounded. Hence, the semiconductor circuit component can take the place of the prior-art mechanical relay without any substantial change of the circuit configuration of the bus bar circuit board.
(9) Further, according to the invention, in the semiconductor circuit component according to as in (1), the drive control circuit has first and second drive control circuits and the switch unit has first and second switch units, the first drive control circuit being connected in series with the first switch unit between the power supply and the ground, the second drive control circuit being connected in series with the second switch unit between the power supply and the ground, so that only when the first and second switch units are turned on, the power supply voltage is supplied from the drive control circuit to the control signal supply circuit.
In this configuration, only when the first and second switch units are turned on simultaneously, the power supply voltage is supplied to the control signal supply circuit. Accordingly, the load can be prevented more surely from malfunctioning due to the switch unit, so that the semiconductor circuit component can take the place of the mechanical relay.
(10) Further, according to the invention, in the semiconductor circuit component as in (9), preferably, the first drive control circuit includes a first drive-control semiconductor switching device with a control terminal, and a first voltage supply circuit for supplying a drive voltage to the control terminal of the first drive-control semiconductor switching device when the first switch unit is turned on and the first voltage supply circuit is supplied with a power supply voltage having a rated value; the second drive control circuit includes a second drive-control semiconductor switching device with a control terminal, and a second voltage supply circuit for supplying a drive voltage to the control terminal of the second drive-control semiconductor switching device when the second switch unit is turned on and the second voltage supply circuit is supplied with a power supply voltage having a rated value; and when the first and second drive-control semiconductor switching devices are supplied with drive voltages from the first and second voltage supply circuits respectively and driven, the power supply voltage is supplied from the first and second drive-control semiconductor switching devices to the control signal supply circuit.
In this configuration, even if leakage resistance generated between contacts of one of the switch units is low, the power supply voltage having a rated value is not supplied to the voltage supply circuit connected to the other switch unit as long as leakage resistance generated between contacts of the other switch unit is high. Hence, the load can be prevented more surely from malfunctioning due to the externally provided switch units, so that the semiconductor circuit component can take the place of the mechanical relay.
(11) Further, according to the invention, in the semiconductor circuit component as in (10), preferably, the first voltage supply circuit includes a first voltage dividing circuit for dividing the power supply voltage supplied through the first switch unit, and a first voltage suppressing circuit for suppressing a partial voltage into a predetermined value, the partial voltage being obtained by the first voltage dividing circuit; and the second voltage supply circuit includes a second voltage dividing circuit for dividing the power supply voltage supplied through the second switch unit, and a second voltage suppressing circuit for suppressing a partial voltage into a predetermined value, the partial voltage being obtained by the second voltage dividing circuit.
In this configuration, even if the leakage resistance generated between contacts of one of the switch units is low, only the power supply voltage with a low value is allowed to be supplied to the voltage supply circuit connected to the other switch unit as long as the leakage resistance generated between contacts of the other switch unit is high. Moreover, the power supply voltage having the low value is further divided. Hence, the drive-control semiconductor switching device is not made electrically conductive, so that the control signal supply circuit is not driven. As a result, the load can be prevented more surely from malfunctioning due to the externally provided switch units, so that the semiconductor circuit component can take the place of the mechanical relay.
(12) According to the invention, in the semiconductor circuit component as in (10) or (11), preferably, the first drive-control semiconductor switching device is formed to have one end connected to a ground end of the control signal supply circuit while the ground end is grounded through the other end of the first drive-control semiconductor switching device, and the second drive-control semiconductor switching device is formed to have one end connected to a power input end of the control signal supply circuit while the power input end is connected to the power supply through the other end of the second drive-control semiconductor switching device, so that when a drive voltage is supplied from the first voltage supply circuit to the first drive-control semiconductor switching device to thereby drive the first drive-control semiconductor switching device and when a drive voltage is supplied from the second voltage supply circuit to the second drive-control semiconductor switching device to thereby drive the second drive-control semiconductor switching device, the power supply voltage is supplied from the first and second drive-control semiconductor switching device to the control signal supply circuit.
In this configuration, when a drive voltage is supplied from the first voltage supply circuit to thereby drive the first drive-control semiconductor switching device, the ground end of the control signal supply circuit is grounded, whereas when a drive voltage is supplied from the second voltage supply circuit to thereby drive the second drive-control semiconductor switching device, the power input end of the control signal supply circuit is connected to the power supply. Thus, the power supply voltage can be supplied to the control signal supply circuit.
(13) According to the invention, the semiconductor circuit component as in (12) further includes: a first externally leading-out terminal connected to a power input end of the first voltage supply circuit while connected to the power supply through the first switch unit; a second externally leading-out terminal connected to a ground end of the second voltage supply circuit while connected to the ground through the second switch unit; a third externally leading-out terminal connected to the other end of the second drive-control semiconductor switching device and to one end of the load-control semiconductor switching device while connected to the power supply; a fourth externally leading-out terminal connected to the other end of the load-control semiconductor switching device while connected to the load; and a fifth externally leading-out terminal connected to the other end of the first drive-control semiconductor switching device while connected to the ground.
In this configuration, for example, the first and second externally leading-out terminals are made to correspond to terminals at opposite ends of a relay coil, the third and fourth externally leading-out terminals are made to correspond to terminals at opposite ends of relay contacts, and the fifth externally leading-out terminal is grounded. Hence, the semiconductor circuit component can take the place of the prior-art mechanical relay without any substantial change of the circuit configuration of the bus bar circuit board.